Fluorescence (TALIF) measurement of atomic hydrogen concentration in a coplanar surface dielectric barrier discharge

Spatially and temporally resolved measurements of atomic hydrogen concentration above the dielectric of coplanar barrier discharge are presented for atmospheric pressure in 2.2% H2/Ar. The measurements were carried out in the afterglow phase by means of two-photon absorption laser-induced fluorescence (TALIF). The difficulties of employing the TALIF technique in close proximity to the dielectric surface wall were successfully addressed by taking measurements on a suitable convexly curved dielectric barrier, and by proper mathematical treatment of parasitic signals from laser–surface interactions. It was found that the maximum atomic hydrogen concentration is situated closest to the dielectric wall from which it gradually decays. The maximum absolute concentration was more than 10^22 m-3. In the afterglow phase, the concentration of atomic hydrogen above the dielectric surface stays constant for a considerable time (10 us - 1 ms), with longer times for areas situated farther from the dielectric surface. The existence of such a temporal plateau was explained by the presented 1D model: the recombination losses of atomic hydrogen farther from the dielectric surface are compensated by the diffusion of atomic hydrogen from regions close to the dielectric surface. The fact that a temporal plateau exists even closest to the dielectric surface suggests that the dielectric surface acts as a source of atomic hydrogen in the afterglow phase

Influence of secondary neutrons induced by proton radiotherapy for cancer patients with implantable cardioverter defibrillators

<p>Abstract</p> <p>Background</p> <p>Although proton radiotherapy is a promising new approach for cancer patients, functional interference is a concern for patients with implantable cardioverter defibrillators (ICDs). The purpose of this study was to clarify the influence of secondary neutrons induced by proton radiotherapy on ICDs.</p> <p>Methods</p> <p>The experimental set-up simulated proton radiotherapy for a patient with an ICD. Four new ICDs were placed 0.3 cm laterally and 3 cm distally outside the radiation field in order to evaluate the influence of secondary neutrons. The cumulative in-field radiation dose was 107 Gy over 10 sessions of irradiation with a dose rate of 2 Gy/min and a field size of 10 × 10 cm². After each radiation fraction, interference with the ICD by the therapy was analyzed by an ICD programmer. The dose distributions of secondary neutrons were estimated by Monte-Carlo simulation.</p> <p>Results</p> <p>The frequency of the power-on reset, the most serious soft error where the programmed pacing mode changes temporarily to a safety back-up mode, was 1 per approximately 50 Gy. The total number of soft errors logged in all devices was 29, which was a rate of 1 soft error per approximately 15 Gy. No permanent device malfunctions were detected. The calculated dose of secondary neutrons per 1 Gy proton dose in the phantom was approximately 1.3-8.9 mSv/Gy.</p> <p>Conclusions</p> <p>With the present experimental settings, the probability was approximately 1 power-on reset per 50 Gy, which was below the dose level (60-80 Gy) generally used in proton radiotherapy. Further quantitative analysis in various settings is needed to establish guidelines regarding proton radiotherapy for cancer patients with ICDs.</p

Evaluación técnica y económica de la suplementación con monensina (Rumensin®) y/o levadura (Yea-Sacc1026) a vacas lecheras

25 p.En el trópico la demanda creciente de alimentos a menor costo incentivó a los investigadores a realizar pruebas con aditivos. Entre abril y agosto de 2001, se estudió en Zamorano el efecto de la adición de levadura (Yea-Sacc1026) y/o monensina sódica (Rumensín®) en 12 vacas con más de 35 días de lactancia al inicio del ensayo. Las vacas fueron estabuladas en corrales con comederos Calan® y ordeñadas dos veces al día. Se usó un diseño experimental de sobrecambio en cuadrado latino, con tres grupos de cuatro vacas que pasaron por los cuatro tratamientos en periodos de 21 días. Hubo una semana de adaptación antes de cada tratamiento. Diariamente se registró la humedad relativa y temperatura ambiental. Se hizo un análisis económico con presupuestos parciales. Los tratamientos fueron: Testigo sin levadura ni monensina, adición de 10 g/vaca/día de levadura, adición de 300 mg/vaca/día de monensina y adición de 10 g de levadura + 300 mg de monensina vaca/día. El consumo de MS/vaca/día fue de 14.6, 14.7, 14.1 y 14.4 kg y el consumo de materia seca (MS) del ensilaje de 6.8, 6.7, 6.1 y 6.4 kg, respectivamente para los cuatro tratamientos. La producción promedio de leche fue de 20.8, 20.6, 20.6 y 20.5 kg/día y el contenido de grasa de 3.22, 3.34, 3.06 y 3.23%, sin diferencias estadística entre los tratamientos (P < 0.05). El peso y la condición corporal de los animales no fue afectada por los tratamientos y fueron en promedio 491 kg y 2.19. La temperatura y humedad relativa no influenciaron la producción de leche. Los tratamientos: levadura y levadura más monensina resultaron dominados económicamente debido a que elevaron los costos variables sin aumentar la producción, monensina tuvo los menores costos variables por el menor consumo de materia seca y el testigo tuvo el mayor beneficio neto. La TRM entre monensima y el testigo fue de 550%, por lo que no se recomienda el uso de aditivos en las condiciones actuales de Zamorano.1. Índice de cuadros 2. Índice de gráficas 3. Índice de anexos 4. Introducción 4. Materiales y métodos 5. Resultados y discusión 6. Conclusiones 7. Recomendaciones 8. Bibliografía 9. Anexo